REDWOOD CITY, Calif.,
March 4, 2013 /PRNewswire/
-- AcelRx Pharmaceuticals, Inc. (Nasdaq: ACRX), a specialty
pharmaceutical company focused on the development and
commercialization of innovative therapies for the treatment of
acute and breakthrough pain, today announced top-line data results
demonstrating that the first of two pivotal placebo-controlled
Phase 3 studies for its investigational sublingual Sufentanil
NanoTab PCA (patient-controlled analgesia) System met its primary
endpoint. Adverse events reported in the study were generally
mild or moderate in nature and similar in both placebo and
treatment groups.

The primary endpoint evaluated pain intensity over the
48-hour study period compared to baseline, or Summed Pain Intensity
Difference (SPID-48), in patients following major open abdominal
surgery. Results demonstrated that patients receiving
sufentanil NanoTabs realized a significantly greater SPID-48 during
the study period than placebo-treated patients (p=0.001).
Secondary endpoint data also showed that 24 hours and 72
hours after first dose, SPID was significantly greater in the
sufentanil-treated patients than in the placebo-treated patients
(p<0.001 and p=0.004
respectively).

"These favorable results enable AcelRx to continue
moving forward towards submission of a New Drug Application (NDA)
for the Sufentanil NanoTab PCA System in the third quarter of this
year," said Richard King, president
and CEO of AcelRx. "In the weeks ahead, our team will work
with the FDA to complete a pre-NDA meeting in support of this
goal."

Phase 3 Study ResultsUtilizing a
randomized, double-blind, placebo-controlled design, this pivotal
Phase 3 study enrolled 178 adult patients at 13 U.S. sites for the
treatment of acute post-operative pain immediately following major
abdominal surgery. Patients were treated for post-operative
pain for a minimum of 48 hours, and up to 72 hours. Patients
were randomized 2:1, with 119 patients randomized to sufentanil and
59 to placebo treatment. Both treatments were delivered by
the patient, as needed, using the NanoTab System with a 20-minute
lock-out period. Patients in both groups could receive up to
2 mg morphine intravenously per hour as a rescue medication, the
primary purpose of this rescue medication being to provide
placebo-treated patients access to pain medication to enable them
to stay in the study as long as possible. Pre-rescue pain
scores were imputed to minimize the impact of this rescue opioid on
efficacy evaluations.

Eighty, or 70.2% of the sufentanil NanoTab-treated
patients completed the 48-hour study period, compared to 30 (51.7%)
placebo-treated patients. Reasons for drop-out in the
sufentanil- and placebo-treated groups were adverse events (5.3%
and 6.9% respectively), lack of efficacy (16.7% and 31.0%
respectively) and other (7.9% and 10.3% respectively). The
primary endpoint measure, SPID-48, was 105.6 for sufentanil-treated
patients and 55.6 for placebo-treated patients (p=0.001).

Treatment-emergent adverse events occurred in 64.0% of
sufentanil-treated patients and 67.2% of placebo-treated
patients. Adverse events with an occurrence greater than 5%
in either the sufentanil group or the placebo group were nausea
(30.7% and 41.4% respectively), fever (14.9% and 8.6%
respectively), vomiting (8.8% and 6.9% respectively), itching (8.8%
and 0.0% respectively), oxygen saturation decrease (6.1% and 1.7%
respectively), and hypertension (2.6% and 5.2% respectively).
Itching, a frequently observed side effect of opioids, was
the only adverse event that was significantly different between the
groups (p=0.017). All reported cases of itching in the
study were mild in nature. Only one patient (in the
sufentanil group) experienced a serious adverse event, which was
determined to be unrelated to the study drug by the
investigator.

"These efficacy and safety results underscore the
impact of the Sufentanil NanoTab PCA System by potentially
providing medical professionals a non-invasive method to help
relieve moderate-to-severe post-operative pain in patients
undergoing major surgical procedures, such as open abdominal
surgery," commented Pamela Palmer
M.D., Ph.D., chief medical officer and AcelRx
co-founder. "We look forward to completing the full analysis
of these data and working with the FDA on the NDA for this
important post-operative pain advancement."

"The positive results to date for this, non-invasive
approach for the management of moderate-to-severe post-operative
pain are intriguing and I look forward to the complete study
results for the entirety of this Phase 3 program," stated study
investigator Dr. Tong-Joo Gan,
Vice-Chair of the Department of Anesthesiology at Duke University School of Medicine, Durham, N.C.

One additional pivotal Phase 3 double-blind,
placebo-controlled study of the Sufentanil NanoTab PCA System is
underway. The study began in August
2012, and is designed to enroll approximately 400 patients
in a 3:1 randomization following hip or knee replacement surgery at
up to 35 sites. The primary endpoint, SPID-48, is identical to the
primary endpoint for the abdominal surgery trial. We expect
top-line results for this trial to be available in the second
quarter of 2013. Additional information can be found by
visiting www.ClinicalTrials.gov and
using the identifier NCT01660763.

About Post-Operative Pain

Acute pain management in the hospital, in particular
post-operative analgesia, remains a challenge for healthcare
providers with up to 75% of patients reporting inadequate pain
relief following surgery. Inadequate treatment of
post-surgical pain can lead to decreased mobility, which increases
the risks for serious medical complications, including deep vein
thrombosis and partial lung collapse, potentially resulting in
extended hospital stays. More than 30 million surgical
procedures per year result in moderate to severe pain in the U.S.
and EU, with an additional 27 million procedures occurring in
countries with moderate to high per capita healthcare expenditures.
The U.S., 5 main EU countries and Japan represented $5.1
billion of acute pain treatment product sales in 2008.
Currently patients experiencing post-operative pain in the
hospital may have IV PCA treatment, typically utilizing morphine or
hydromorphone. However, there are deficiencies associated
with the current use of IV PCA that can negatively impact patient
safety, well-being and recovery. These include drug-related
side effects associated with morphine or hydromorphone,
complications associated with IV delivery, and medication delivery
errors typically associated with misprogramming of the complex IV
PCA pumps.

About the Sufentanil NanoTab PCA SystemThe
NanoTab System is an investigational pre-programmed, non-invasive,
handheld system that allows post-operative patients to self-dose
with sublingual Sufentanil NanoTabs to manage their post-operative
pain. The NanoTab System is designed to address the
limitations of IV PCA by offering:

A high therapeutic index opioid: The NanoTab System uses the
high therapeutic index opioid sufentanil; it offers post-operative
pain patients the potential for effective patient-controlled
analgesia with a low incidence of drug-related side effects.

A non-invasive route of delivery of analgesia: The sublingual
route of delivery used by the NanoTab System provides rapid onset
of analgesia, therefore eliminating the risk of IV-related
analgesic gaps and IV complications, such as catheter-related
infections, associated with IV PCA delivery. In addition, because
patients are not tethered to IV tubing and a pump for pain relief,
the NanoTab System allows for ease of patient mobility.

A simple, pre-programmed PCA solution: The NanoTab System is
pre-programmed, and thereby eliminates the risk of pump programming
errors by healthcare providers.

Conference Call AcelRx will conduct a
conference call and webcast tomorrow morning, March 5, 2013, at 8:30
a.m. Eastern time (5:30 a.m. Pacific
time) to discuss the Phase 3 top-line results. To
listen to the conference call, dial in approximately ten minutes
before the scheduled call to (800) 860-2442 for domestic callers,
(866) 605-3852 for Canadian callers, or (412) 858-4600 for
international callers. Those interested in listening to the
conference call live via the Internet may do so by visiting the
Investor Relations section of the company's website at www.acelrx.com.

About AcelRx Pharmaceuticals, Inc. AcelRx
Pharmaceuticals, Inc. is a specialty pharmaceutical company focused
on the development and commercialization of innovative therapies
for the treatment of acute and breakthrough pain. AcelRx's
lead product candidate, the ARX-01 Sufentanil NanoTab PCA System,
is designed to solve the problems associated with post-operative
intravenous patient-controlled analgesia which has been shown to
cause harm to patients following surgery because of the side
effects of morphine, the invasive IV route of delivery and the
complexity of infusion pumps. ARX-01 has successfully
completed two of its three planned Phase 3 clinical trials and a
New Drug Application submission is planned for the third quarter of
2013. AcelRx recently completed enrollment in a Phase 2 study for
ARX-04, a sufentanil formulation for the treatment of
moderate-to-severe acute pain, funded through a grant from U.S.
Army Medical Research and Materiel Command, and top-line results
are expected in the second quarter of 2013. The company has
two additional pain treatment product candidates, ARX-02 and
ARX-03, which have completed Phase 2 clinical development.
For additional information about AcelRx's clinical programs
please visit www.acelrx.com.

Forward Looking Statements This press
release contains forward-looking statements, including, but not
limited to, statements related to the process and timing of
anticipated future clinical development of AcelRx Pharmaceuticals'
product candidates, including the release of sufentanil NanoTab PCA
System top-line clinical trial data, the release and anticipated
timing of additional NanoTab System clinical trial data, the
potential submission of an NDA for NanoTab System and the timing
thereof, therapeutic and commercial potential of NanoTab System and
the anticipated timing and therapeutic and commercial potential of
other AcelRx Pharmaceuticals' product candidates. These
forward-looking statements are based on AcelRx Pharmaceuticals'
current expectations and inherently involve significant risks and
uncertainties. AcelRx Pharmaceuticals' actual results and the
timing of events could differ materially from those anticipated in
such forward-looking statements as a result of these risks and
uncertainties, which include, without limitation, risks related to:
the ability of AcelRx Pharmaceuticals to successfully complete the
clinical trials for the sufentanil NanoTab System, that fact that
subsequent analyses of the top-line data may lead to different
(including less favorable) interpretations of the results than the
analyses conducted to date or may identify important implications
of the study that are not reflected in these statements, or be
subject to differing interpretations by the regulatory agencies;
the success, cost and timing of all product development activities
and clinical trials; the uncertain clinical development process,
including the risk that clinical trials, have an effective design,
enroll a sufficient number of patients, or be completed on
schedule, if at all; any delays or inability to obtain and maintain
regulatory approval of its product candidates in the United States and Europe; its ability to obtain adequate
clinical supplies of the drug and device components of its product
candidates; its ability to attract funding partners or
collaborators with development, regulatory and commercialization
expertise; its ability to obtain sufficient financing to complete
registration of its product candidates in the United States and Europe; the market potential for its product
candidates; the accuracy of AcelRx Pharmaceuticals' estimates
regarding expenses, capital requirements and needs for financing;
and other risks detailed in the "Risk Factors" and elsewhere in
AcelRx Pharmaceuticals' U.S. Securities and Exchange Commission
filings and reports, including its Current Report on Form 8-K filed
with the SEC on December 7, 2012.
AcelRx Pharmaceuticals undertakes no duty or obligation to
update any forward-looking statements contained in this release as
a result of new information, future events or changes in its
expectations.

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